The invention relates to a hearing aid which is insertable in the outer auditory canal. A typical hearing aid of this type is disclosed in Great Britain patent application No. 20 70 890.
In hearing aids insertable into the auditory canal, which are referred to as canal hearing aids, the space available for the assembly of the hearing aid components is extremely limited. The configuration of the various parts is therefore very important. In the hearing aid according to Great Britain patent application No. 20 70 890, the largest component (i.e. the power source) is mounted in a depression in the outside wall which terminates the housing towards the outside, in order to place it where the auditory canal usually has its largest diameter. Since this large diameter is usually not very deep, the flat area of the power source was placed parallel to the end wall. But a hinged cover was used for the end wall to obtain a straight outer surface. This, however, has the disadvantage that there is little opportunity to grip the instrument to pull it out of the ear. Moreover, room is lacking for providing, next to the usual volume control, an additional control which permits adaptation of the amplification characteristic of the instrument to an individual hearing impairment, etc.
In instruments disclosed by U.S. Pat. No. 2,987,584 a hinged cover is used for the mounting space of the power source. When this cover is opened, it can serve as a handle to pull the instrument out of the ear. Deviating from the above mentioned approach, clamping the power source inside the housing is not possible in a canal hearing aid because such a holding means requires space on the one hand, and because it is very difficult to remove the power source located inside the housing on the other. Therefore, in other hearing aids such as those disclosed in European patent application E-PA-O 0 085 032, the idea of mounting the battery inside the housing has been abandoned; but this results in the possibility that the battery can get lost when the instrument is pulled out of the ear by its cover. Furthermore, no adjustment of the amplification characteristics is possible in this embodiment.